There are situations in which false excitations of a slip control system can occur, if for example the oscillations in a wheel speed signal of a vehicle wheel are falsely interpreted as slip, and the slip control system responds thereto with slip control.
Such wheel oscillations can occur for example owing to a relative displacement between the wheel suspension with vibration damping and the structure of the vehicle, and indeed not only owing to a vertically running spring travel, but also owing to spring travel in the longitudinal direction of the vehicle. If the vehicle wheel is displaced in the longitudinal direction of the vehicle, then the detected wheel speed changes because of the displacement relative to the structure of the vehicle. Said difference between the wheel speed and the speed of the vehicle can result in falsely detected slip. Furthermore, it has been determined that such a vibration of the vehicle wheel in the longitudinal direction of the vehicle can be initiated by a rapid modulation of the brake pressure at the wheel brake of the vehicle wheel. Therefore, it must be assumed therefrom that a rapid rise in brake pressure can result in oscillations of the wheel speed signal and therefore there is a risk that the slip control falsely detects such a wheel state as slip.
Therefore, such a slip control system must recognize an actual slip and must determine the value thereof very accurately.
Thus, there is a conflict with slip control, whereby on the one hand said slip control should already be used sensitively for a small slip in order to avoid large slips, followed by deep pressure reduction phases, and to avoid an inhomogeneous deceleration profile, but on the other hand the slip control may not be triggered falsely, if for example the slip detected by the slip control system is only the result of a wheel vibration and said detected “slip” would also disappear without slip control. The conflict is that the first objective of sensitive slip control requires sensitive slip control thresholds, whereas the second objective to avoid a “phantom slip” would require insensitive slip control thresholds.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.